This invention relates to forming a continuous reinforced composite material.
Reinforced composite materials (e.g., reinforced thermoplastics) are used in a wide variety of industrial, transportation, and engineering applications. For example, composite materials may be used for lining containers (e.g., cargo hulls and landfills) or for covering, protecting, and containing materials (e.g., during transportation in ships, trucks, and rail cars, and during storage either within or outside containers). Reinforced thermoplastics may be made with a reinforcing grid interposed between two or more polymer films to enhance the physical properties of the thermoplastic material. The reinforcing grid is typically a scrim of woven or nonwoven fabric around which the polymer films are bonded or laminated.
The reinforced laminates are typically manufactured as mill roll goods in a variety of widths and lengths depending on the machine or machines involved in the lamination process. Typical roll good widths may range from one to twenty feet, while roll good lengths may vary from one hundred to ten thousand feet. In many applications, the surface area to be lined or covered exceeds the size or is incompatible with the shape in which sections of the reinforced thermoplastic material may be economically manufactured. In such cases, the reinforced laminates are seamed together to achieve the desired shape and size. The reinforced laminates are first overlapped to the extent necessary for a particular seaming process (e.g., heat, hot air, wedge, or radio frequency). A seam is then formed by bonding the two reinforced laminates together to create a continuous reinforced composite material. However, when using existing reinforced composite materials and methods of seaming, the seam may not retain the performance characteristics (e.g., tear resistance) of the individual sections of the reinforced laminate, thereby leading to areas having increased susceptibility to operational failure.
For example, referring to FIG. 10, two sheets of reinforced thermoplastic material 20, 25 may be overlapped and coupled to form a seam 30. Each sheet of reinforced thermoplastic material 20, 25 may include two or more layers of a polymer film 31, 32 between which is coupled a scrim 35 of horizontal reinforcing fibers 39, 40 (i.e., oriented in the width or fill direction of the mill roll good) and longitudinal reinforcing fibers 45, 46 (i.e., oriented in the linear or machine direction of the mill roll good). During manufacture, the scrim 35 of the reinforced thermoplastic material 20, 25 extends across the width of the mill roll good such that the horizontal reinforcing fibers 39, 40 terminate in free ends 41a, 41b.
When a seam 30 is formed by overlapping the borders 42, 43 containing the horizontal reinforcing fibers 39, 40 having free ends 41a, 41b, the tensile strength of the seamed material may be reduced significantly (e.g., approximately 30%) as compared to the individual sheets. The strength of the seam 30 is dependent primarily on the type of seam created, the width of the seam, and the bonding properties of the polymer films and not the strength of the reinforcing fibers of the scrim. Therefore, referring to FIGS. 11, 12 and 13, a seam 50 formed between two sheets of such a reinforced thermoplastic material 55, 60 may demonstrate horizontal and/or longitudinal fiber pull from the seam and separation when exposed to longitudinal, horizontal, and diagonal tensile forces, (e.g., as depicted by arrows 61a, 61b, 62a, 62b, 63a, and 63b, respectively). The separation of the reinforcing fibers renders the seamed material susceptible to operational failure.